Which grain is the only one to turn inside out?
Popcorn is the only grain that turns completely inside out when it pops.
When heated, moisture inside the kernel turns to steam and builds pressure until the hull bursts. The internal starch instantly expands into a fluffy foam, completing the flip in just 10 milliseconds. This is faster than the blink of an eye and leaves the original outer shell trapped inside the soft starch.
Nerd Mode
Popcorn (Zea mays everta) is unique among corn varieties because its hull, or pericarp, is unusually thick and strong. This allows the kernel to function like a natural pressure cooker. Inside the kernel is a small droplet of water stored within a circle of soft starch. As the kernel reaches approximately 355 degrees Fahrenheit (180 degrees Celsius), the internal water turns into pressurized steam.The pressure builds to about 135 pounds per square inch before the hull finally ruptures. At this critical moment, the pressurized steam expands rapidly, and the starch gelatinizes into a hot, bubbly foam. This process happens with such force that the entire structure turns inside out. Researchers at the French National Center for Scientific Research used high-speed cameras to record this event in 2015.The study confirmed that the entire physical transformation occurs in roughly 0.01 seconds. The 'pop' sound heard during the process is not the hull breaking, but the sudden release of air pressure from the kernel. This rapid expansion creates the white, crunchy structure we eat, which is essentially solidified starch foam. While other grains like rice or wheat can puff, they do not possess the structural integrity to invert completely like popcorn.
Verified Fact
FP-0002472 · Feb 16, 2026